1. Field of the Invention
This invention relates to a liquid crystal projector, a method of projecting an image by use of a liquid crystal light valve panel, and more particularly to a color liquid crystal projector using a photoconductive type liquid crystal light valve panel or panels.
2. Description of the Related Art
A color liquid crystal projector has a light source for emitting a white light, a first dichroic mirror adapted for allowing a R(Red) component of the emitted white light to be reflected and allowing other components i.e. G (Green) and B (Blue) components, to be transmitted therethrough, and a second dichroic mirror adapted for allowing the G component of the transmitted light to be reflected and allowing the remaining B component to be transmitted therethrough. The white light is thus separated into R, G and B components by these dichroic mirrors.
The color liquid crystal projector also has three liquid crystal light valve panels for R, G and B components adapted to respectively modulate R, G and B components, and a controller adapted for outputting video (image) data from the external as write data D.sub.R, D.sub.G and D.sub.B for every R, G and B component. The color liquid crystal projector further has a first writing CRT (Cathode Ray Tube) adapted to emit a writing light for writing an image corresponding to the R-component of the video data onto the R-component liquid crystal light valve panel on the basis of the write data D.sub.R, a second writing CRT adapted to emit a writing light for writing an image corresponding to the G-component of the video data onto the G-component liquid crystal light valve panel on the basis of the write data D.sub.G, and a third writing CRT adapted to emit a writing light for writing an image corresponding to the B-component of the video data onto the B-component liquid crystal light valve panel on the basis of the write data D.sub.B. Light modulations corresponding to video data are carried out with respect to R, G and B components, respectively.
The color liquid crystal projector further has an optical system adapted to combine three rays of light respectively modulated by the three liquid crystal light valve panels to project an image corresponding to the combined light in an enlarged manner onto a screen. Thus, a color image corresponding to the video data can be obtained on the screen.
In the above-mentioned color liquid crystal projector, since three sets of writing CRTs and liquid crystal light valve panels are used to form an image, there is a problem that the structure of the projector becomes large, and a high assembling accuracy is required, resulting in an increased cost. Further, there is an inconvenience that the back focus or back focal distance (the length from the projection lens to the liquid crystal light valve panel) is elongated, so that the optical system including lens, polarization beam splitter, and the like becomes large, resulting in an increased cost. Furthermore, there is an inconvenience that the degree of freedom in design of the lens is lowered. In addition, since three images are synthesized to provide one color image, it is difficult to obtain an image of high fineness.